Zirconium-based metallic glass and zirconia coatings to inhibit bone formation on titanium.

Surface-modified commercially pure titanium (Cp-Ti) with zirconium (Zr)-based thin film metallic glasses (Zr-TFMGs) and ZrO2 thin films were surgically implanted into the tibiae of rats; the bone formation was analyzed to examine the performance of the coatings as a biomaterial. Zr-TFMGs and ZrO2 thin films were coated on Cp-Ti substrates to monitor the control of assimilation in vitro and in vivo. The microstructural and elemental analyses were carried out for the as deposited thin films by x-ray diffraction (XRD), transmission electron microscopy and x-ray photoelectron spectroscopy. TFMG- and ZrO2-coated Ti specimens were immersed in simulated body fluid (SBF) for a period of 21 days to evaluate the calcium phosphate precipitation in vitro. XRD, x-ray photoelectron spectroscopy and scanning electron microscopy/energy dispersive x-ray spectroscopy were used to quantify the mineralization on the coated Zr-TFMG and ZrO2. In vitro corrosion studies showed that the Zr-based TFMG and ZrO2 coatings sustained in the SBF, exhibited superior corrosion resistance to the bare crystalline Ti substrate. Wettability studies showed TFMG and ZrO2 coatings with a hydrophobic nature, and the TFMG-coated SBF-submerged specimens showed a hydrophilic nature. The in vitro cell viability of MC3T3-E1 cells showed good cell proliferation and low cytotoxicity. The calcification deposits were evaluated by staining with alizarin red S, which showed a lower calcium formation on Zr-TFMG compared to ZrO2. The present work also aims to assess the assimilation behavior of Cp-Ti, Zr-TFMG and ZrO2 in vivo by inserting the coated specimen in the femur of rats. After post-implantation of 8 weeks, specimens were examined by micro-CT evaluation. The bone contact ratios as calculated were 72.75%, 15.32% and 38.79%. Consequently, the bone affinity was Cp-Ti wire >ZrO2-coated Ti wire >Zr48Cu36Ag8Al8-coated Ti wire.

Surface characterization of commercially available yttria-stabilized tetragonal zirconia polycrystalline in water and Hanks' solution using X-ray photoelectron spectroscopy.

To elucidate the mechanism of adhesion of soft and hard tissues to yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP), Y-TZP and titanium disks were immersed in ultrapure water and in Hanks' solution, and the changes in the surface compositions and chemical states were characterized using X-ray photoelectron spectroscopy. After immersion in ultrapure water for 60 days, the concentration of hydroxyl groups on the Y-TZP surface increased. In addition, only phosphate ions were incorporated into the surface during immersion in Hanks' solution, while other ions did not react. On the other hand, the surface of Ti was also hydrated in ultrapure water; however, calcium phosphate formed on it during immersion in Hanks' solution. Therefore, the reactivity of Y-TZP with electrolytes was lower than that of Ti. We conclude that the formation of the phosphate on the Y-TZP surface in physiological conditions possibly enhances the adhesion of soft and hard tissues to Y-TZP.

Enhanced biological fixation of ligaments to bone tissues utilizing chitin fabrics.

In ligament reconstruction involving anterior cruciate ligament surgery, biological fixation between the transferred ligament and bone tissue is critical for achieving successful outcomes. Here, we administered chitin fabrics into the bone tunnels and evaluated their efficacy in promoting biological fixation. An animal model on the rat's patellar ligament was employed. First, bone tunnels were created in the lateral condyle of the femur. The ligament was then separated from the tibial tuberosity, and half was inserted into the tunnel and fixed with the use of end button. Animals in the experimental group were treated with microfiber nonwoven chitin fabric, whereas control animals received no treatment. Specimens were collected at 2, 4, and 6 weeks after surgery, and the fixation strength was measured by mechanical tests. Histological sections were prepared from samples prepared 4 weeks after surgery, and the diameter of bone tunnel and the width ratio of collagenous tissue in the bone tunnel were measured. Administration of chitin significantly increased the mean fixation strength at 4 and 6 weeks after surgery. Furthermore, chitin also promoted bone formation in the bone tunnel and increased the density of collagen fibers. Thus, microfiber nonwoven chitin fabric enhanced the biological fixation of the ligament to the bone tissue. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2355-2360, 2018.

Enhanced bone formation in the vicinity of porous ß-TCP scaffolds exhibiting slow release of collagen-derived tripeptides.

It has been experimentally proven that orally ingested collagen-derived tripeptides (Ctp) are quickly absorbed in the body and effectively promote the regeneration of connective tissues including bone and skin. Ctp are capable to activate osteoblasts and fibroblasts, which eventually promotes tissue regeneration. Based on these findings, a hypothesis was formulated in this study that direct delivery of Ctp to bone defect would also facilitate tissue regeneration as well as oral administration. To test the hypothesis, we prepared a bone augmentation material with the ability to slowly release Ctp, and investigated its in vivo bone regeneration efficacy. The implant material was porous ß-tricalcium phosphate (ß-TCP) scaffold which was coated with a co-precipitated layer of bone-like hydroxyapatite and Ctp. The ß-TCP was impregnated with approximately 0.8%(w/w) Ctp. Then, the Ctp-modified ß-TCP was implanted into bone defects of Wistar rats to evaluate in vivo efficacy of Ctp directly delivered from the material to the bone defects. The control was pristine porous ß-TCP. In vitro tests showed that Ctp were steadily released from the co-precipitated layer for approximately two weeks. The Ctp-modified scaffolds significantly promoted new bone formation in vivo in their vicinity as compared with pristine ß-TCP scaffolds; 6 weeks after the implantation, Ctp-modified scaffolds promoted twice as much bone formation as the control implants. Consequently, we achieved the slow and steady release of Ctp, and found that direct delivery of Ctp from implant materials was effective for bone regeneration as well as oral administration. A ß-TCP scaffold capable of slowly releasing bone-enhancing substances significantly promoted bone formation.

Comparison of nerve regenerative efficacy between decellularized nerve graft and nonwoven chitosan conduit.

BACKGROUND: Recently decellularized nerves with various methods are reported as highly functional nerve grafts for the treatment of nerve defects. OBJECTIVE: To evaluate the efficacy of decellularized allogeneic nerve, compared with oriented chitosan mesh tube, and an autologous nerve. METHODS: Sciatic nerves harvested from Sprague-Dawley (SD) rats were decellularized in combination with Sodium dodecyl sulfate and Triton X-100. A graft into the sciatic nerve in Wistar rats was performed with the decellularized SD rat sciatic nerves or oriented chitosan nonwoven nanofiber mesh tubes (15 mm in length, N=5 in each group). A portion of sciatic nerve of Wistar rat was cut, reversed and re-sutured in-situ as a control. Nerve functional and histological evaluations were performed 25 weeks postoperatively. RESULTS: It was revealed that functional, electrophysiological and histological recoveries in the decellularized nerve group match those in the autograft group. Recovery of sensory function and nerve maturation in the decellularized nerve group were superior to those in the chitosan mesh tube group. CONCLUSIONS: Nerve regeneration in the decellularized nerves could match that in the autografts and is somehow superior to artificial chitosan mesh tube. Detergents wash of SDS and Triton X-100 could obtain highly functional nerve grafts from allografts.